There are many techniques by which a liquid which is dispersed and insoluble (i.e., the dispersed liquid) within another liquid (i.e., the continuous phase liquid) can be separated from one another. While the separation of two liquids can be effected by taking advantage of the differences in buoyancy or specific gravity of the two liquids, many such liquid dispersions are so stable that such a buoyancy separation cannot be efficiently carried out in a reasonable period of time.
One technique which can be used in conjunction with other techniques such as buoyancy separation to efficiently separate such liquids within a reasonable time is known as coalescence. The technique of coalescence involves contacting a porous medium with the two liquids under certain conditions such that both liquids pass through the porous medium but such that the particles of the dispersed liquid are combined to form larger particles, i.e., the dispersed liquid coalesces. After passage through the porous medium, other techniques, such as separation effected by buoyancy in view of the difference in specific gravities of the two liquids, can be efficiently used to complete the separation of the two liquids in a reasonable time.
Milk is a fine dispersion of water-insoluble butterfat in a continuous aqueous phase of the milk. For many purposes, it is desirable to remove as much of the butterfat from the milk as possible, and the milk processing industry currently uses a mechanical apparatus, e.g., a cream separator, to separate the heavy cream, which includes butterfat, from whole milk. This process produces skim milk which generally contains an average of about 0.06 wt. % butterfat. The cream separator, however, is not particularly well-suited to efficiently reduce the butterfat content of milk to even lower levels.
Thus, there is a need for an efficient process to reduce the butterfat content of milk, particularly skim milk and buttermilk, and milk products such as whey. The present invention provides such a method of reducing the butterfat content of milk products through the use of coalescence technology. Surprisingly, despite the fine dispersion of butterfat within milk, particularly within skim milk and homogenized milk, it has been found that, under certain conditions, coalescing technology can be quite useful in effecting the separation of butterfat from milk. Moreover, the present inventive method is capable of doing so at reasonable flow rates and applied pressures. These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.